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R Shane Tubbs

Publications and source records attributed to R Shane Tubbs.

At least 19 recordsLinked to original sources
PubMed2007

Observations at the craniocervical junction with simultaneous caudal traction of the spinal cord.

INTRODUCTION: Some have opined that caudal traction of the spinal cord may result in caudal descent of the hindbrain. MATERIALS AND METHODS: In fresh adult cadavers (n = 12; less than 6 h postmortem) with no CIM, distal tension (75 N) was applied to the conus medullaris with simultaneous observation of the cervical spinal cord, brainstem, and hindbrain and their relationship to the foramen magnum per occipital craniectomy and removal of the posterior arch of C1. RESULTS: After lumbar laminectomy in cadavers, caudal tension on the cord (conus medullaris) demonstrated negligible movement (less than 1 mm) of the caudal brain stem and cervical spinal cord. No movement of the cerebellar tonsils was identified. Moreover, after transection of the lumbar dural cul-de-sac and lumbar spinal dural nerve sleeves, distal traction produced only 2 to 3 mm of caudal descent of the brain stem and cervical spinal cord. Again, no movement of the cerebellar tonsils was visualized. CONCLUSIONS: Our findings in a fresh cadaveric model suggest that it is unlikely that caudal fixation of the distal spinal cord results in inferior displacement of the cerebellar tonsils, and a resultant Chiari I malformation or that transection of the filum terminale may reverse tonsillar ectopia. In vivo animal studies are now necessary to verify our findings.

Aged↗
PubMed2007

Split spinal cord malformation.

The split spinal cord is a rare congenital malformation. We report the rare finding of a split cord malformation in a young girl. Further evaluation of this anomaly revealed a Type I split cord malformation (midline bony septation), with no other concomitant pathological entities. Various hypotheses have been made regarding the embryology of this unusual form of spinal dysraphism, and these are reviewed along with the common clinical manifestations of this intriguing pathological entity.

Child↗
PubMed2007

Right-sided vagus nerve stimulation inhibits induced spinal cord seizures.

We have previously shown that left-sided vagus nerve stimulation results in cessation of induced spinal cord seizures. To test our hypothesis that right-sided vagus nerve stimulation will also abort seizure activity, we have initiated seizures in the spinal cord and then performed right-sided vagus nerve stimulation in an animal model. Four pigs were anesthetized and placed in the lateral position and a small laminectomy performed in the lumbar region. Topical penicillin, a known epileptogenic drug to the cerebral cortex and spinal cord, was next applied to the dorsal surface of the exposed cord. With the exception of the control animal, once seizure activity was discernible via motor convulsion or increased electrical activity, the right vagus nerve previously isolated in the neck was stimulated. Following multiple stimulations of the vagus nerve and with seizure activity confirmed, the cord was transected in the midthoracic region and vagus nerve stimulation performed. Right-sided vagus nerve stimulation resulted in cessation of spinal cord seizure activity in all animals. Transection of the spinal cord superior to the site of seizure induction resulted in the ineffectiveness of vagus nerve stimulation in causing cessation of seizure activity in all study animals. As with left-sided vagus nerve stimulation, right-sided vagus nerve stimulation results in cessation of induced spinal cord seizures. Additionally, the effects of right-sided vagus nerve stimulation on induced spinal cord seizures involve descending spinal pathways. These data may aid in the development of alternative mechanisms for electrical stimulation for patients with medically intractable seizures and add to our knowledge regarding the mechanism for seizure cessation following peripheral nerve stimulation.

Animals↗
PubMed2007

Forces necessary for the disruption of the cisternal segments of cranial nerves II through XII.

Manipulation of the cisternal segment of cranial nerves is often performed by the neurosurgeon. To date, attempts at quantifying the forces necessary to disrupt these nerves in situ, to our knowledge, has not been performed. The present study seeks to further elucidate the forces necessary to disrupt the cranial nerves while within the subarachnoid space. The cisternal segments of cranial nerves II through XII were exposed in six unfixed cadavers, all less than 6 hr postmortem. Forces to failure were then measured. Mean forces necessary to disrupt nerves for left sides in increasing order were found for cranial nerves IX, VII, IV, X, XII, III, VIII, XI, VI, V, and II, respectively. Mean forces for right-sided cranial nerves in increasing order were found for cranial nerves IX, VII, IV, X, XII, VIII, V, VI, XI, III, and II, respectively. Overall, cranial nerves requiring the least amount of force prior to failure included cranial nerves IV, VII, and IX. Those requiring the highest amount of force included cranial nerves II, V, VI, and XI. There was an approximately ten-fold difference between the least and greatest forces required to failure. Cranial nerve III was found to require significantly (P < 0.05) greater forces to failure for right versus left sides. To date, the neurosurgeon has had no experimentally derived data from humans for the in situ forces necessary to disrupt the cisternal segment of cranial nerves II through XII. We found that cranial nerve IX consistently took the least amount of force until its failure and cranial nerve II took the greatest. Other cranial nerves that took relatively small amount of force prior to failure included cranial nerves IV and VII. Although in vivo damage can occur prior to failure of a cranial nerve, our data may serve to provide a rough estimation for the maximal amount of tension that can be applied to a cranial nerve that is manipulated while within its cistern.

Aged↗
PubMed2007

Quantitation of and measurements utilizing the sphenoid ridge.

The sphenoid ridge (posterior aspect of the lesser wings) is encountered in many intracranial procedures. Increased knowledge of its morphology and relationships is, therefore, of importance to the neurosurgeon and clinician who appreciate imaging of this anatomical region. We have quantitated this part of the sphenoid bone in dry human skulls (35) and made cadaveric (15) measurements between its parts and surrounding neuroanatomical structures in all three cranial fossae. The length of the left and right lesser wings was on average 4.2 and 4 cm, respectively. The mean widths of this bony part at its midline, midpoint, and lateral point (crista alaris) were 1.5 cm, 2.0 cm, and 2 mm, respectively. From the crista alaris the mean distances to the crista galli, V3 at its exit through the foramen ovale, entrance of the occulomotor nerve into the cavernous sinus, middle meningeal artery at its emergence from the foramen spinosum, and the facial and vestibulocochlear nerves at the internal auditory meatus were 4.9, 4.5, 5, 4.7, and 6.1 cm, respectively. From the midpoint of the lesser wing, the mean distances to the crista galli, V3 at its exit through the foramen ovale, entrance of the occulomotor nerve into the cavernous sinus, middle meningeal artery at its emergence from the foramen spinosum, and the facial and vestibulocochlear nerves at the internal auditory meatus were 4.2, 2.9, 3, 3.4, and 4.7 cm, respectively. From the anterior clinoid process of the lesser wing, the mean distances to the crista galli, V3 at its exit through the foramen ovale, entrance of the oculomotor nerve into the cavernous sinus, middle meningeal artery at its emergence from the foramen spinosum, and the facial and vestibulocochlear nerves at the internal auditory meatus were 4.3, 2.8, 1, 3.3, and 4.1 cm, respectively. Additional measurements between the parts of the sphenoid ridge and surrounding anatomical structures may assist the surgeon who operates in this region or the clinician who view imaging of this anatomy.

Aged↗
PubMed2007

Does the mendosal suture exist in the adult?

There is a paucity of information in the literature regarding the mendosal suture. Furthermore, reports of the closure of this presumed suture of childhood are variable. This study seeks to establish the presence or absence of this structure in the adult. Fifty adult skulls were evaluated for the presence or absence of the mendosal suture. Sixteen percent of specimens were found to have a mendosal suture. Six specimens were found to have these sutures bilaterally, and two had sutures on the right side only. Most sutures were linear in nature. The mendosal suture approximated the superior nuchal line in all specimens and more or less traveled medial and perpendicular to the lambdoidal suture. The length of these sutures ranged from 0.8 to 1.4 cm (1.1 cm). Our hopes are that these data will prove useful to both the anatomist and clinicians, so that, when present, misinterpretation of the mendosal suture will be avoided.

Adult↗
PubMed2007

Landmarks for the identification of the cutaneous nerves of the occiput and nuchal regions.

Although surgical procedures are often performed over the posterior head and neck, surgical landmarks for avoiding the cutaneous nerves in this region are surprisingly lacking in the literature. Twelve adult cadaveric specimens underwent dissection of the cutaneous nerves overlying the posterior head and neck, and mensuration was made between these structures and easily identifiable surrounding bony landmarks. All specimens were found to have a third occipital nerve (TON), lesser occipital nerve (LON), and greater occipital nerve (GON), and we found that the TON was, on average, 3 mm lateral to the external occipital protuberance (EOP). Small branches were found to cross the midline and communicate with the contralateral TON inferior to the EOP in the majority of sides. The mean diameter of the main TON trunk was 1.3 mm. This trunk became subcutaneous at a mean of 6 cm inferior to the EOP. The GON was found to lie at a mean distance of 4 cm lateral to the EOP. On all but three sides, a small medial branch was found that ran medially from the GON to the TON approximately 1 cm superior to a horizontal line drawn through the EOP. The GON was found to pierce the semispinalis capitis muscle on average 2 cm superior to the intermastoid line. The mean diameter of the GON was 3.5 mm. The GON was found to branch into medial and lateral branches on average 0.5 cm superior to the EOP. The LON was found to branch into a medial and lateral component at approximately the midpoint between a horizontal line drawn through the EOP and the intermastoid line. The main LON trunk was found on average 7 cm lateral to the EOP. In specimens with a mastoid branch of the great auricular nerve (GAN), this branch was found at a mean of 9 cm lateral to the EOP. The main trunk of this branch of the GAN was found to lie on average 1 cm superior to the mastoid tip. Easily identifiable bony landmarks for identification of the cutaneous nerves over the posterior head and neck can aid the surgeon in more precisely identifying these structures and avoiding complications. Although the occipital nerves were found to freely communicate with one another, avoiding the main nerve trunks could lessen postoperative or postprocedural morbidity. Moreover, clinicians who need to localize the occipital nerves for the treatment of occipital neuralgia could do so more reliably with better external landmarks.

Aged↗
PubMed2007

The tectorial membrane: anatomical, biomechanical, and histological analysis.

There is minimal information in the literature regarding the tectorial membrane. Further, information in the literature regarding the anatomy and function of this structure is often contradictory. We performed the current study to elucidate further this structure's detailed anatomy, function, and histology. Thirteen adult cadavers underwent dissection of their tectorial membranes and detailed observations and measurements were made of them. Ranges of motion of the craniocervical junction were performed before and after transection of this structure. Histological analysis was performed on all membranes. The tectorial membrane was found to attach much more superiorly than previously described and was found to be firmly adherent to the cranial base and body of the axis but not to the posterior aspect of the odontoid process. The mean thickness of this membrane was found to be 1 mm. Flexion of the head made the tectorial membrane fully taut at 15 degrees and extension made it fully taut at 20 degrees; however, there was a buckling effect (redundant tectorial membrane) noted at the level of the odontoid process in extension. With the alar and transverse ligaments cut and with flexion of the head, the middle portion of this membrane was stretched over the odontoid process, thus acting as a "hammock" that inhibited the odontoid process from moving posteriorly. The tectorial membrane did not limit cervical flexion per se but rather helped to insure that the odontoid process did not impinge into the cervical canal. Lateral flexion was not found to be limited by this structure. Histologically, parallel collagen fibers with spindle-shaped fibrocytes were observed within this membrane and near its attachment to the posterior axis, the collagen fibers were noted to be more homogenous with larger non-spindled fibrocytes. At the cranial attachment of the tectorial membrane, multiple calcified areas were noted that interdigitated with the underlying bone. Also near this cephalic bony attachment, there was an increase in the number of elastic fibers, which were found running parallel with the surrounding Type III collagen fibers. The tectorial membrane was found to attach much more superiorly than previously described. We would propose that the tectorial membrane provides for a second line of defense, preventing the odontoid process from compressing the spinal cord and by doing so, secondarily limits movement of the craniocervical juncture. This hypothesis is strengthened by the finding of many elastic fibers in the tectorial membrane. To our knowledge, our study is the first to perform a detailed histological analysis of the tectorial membrane. We hope that these data are useful to the clinician who investigates this ligament of the craniocervical region.

Aged↗
PubMed2007

An unusual course of the left recurrent laryngeal nerve.

Variation in the course of the left recurrent laryngeal nerve is seemingly very rare. During the routine dissection of an adult male cadaver, the entire left recurrent laryngeal nerve after branching from the left vagus nerve was noted to travel medial to the ligamentum arteriosum. We hypothesize that this rare variation may occur, if the left recurrent laryngeal nerve passes inferior to the fifth rather than the sixth aortic arch during embryological development. As our case report demonstrates, the relationship between the ligamentum arteriosum and the left recurrent laryngeal nerve is not absolute. Although seemingly rare, cardiothoracic surgeons must consider variations of the left recurrent laryngeal nerve during surgical procedures in the region of the ligamentum arteriosum in order to minimize potential postoperative complications.

Adult↗
PubMed2007

The oblique cord of the forearm in man.

There is minimal and often conflicting data in the literature regarding the oblique cord of the forearm. The current study seeks to elucidate further the anatomy of this structure of the upper extremity. In adult cadavers, the oblique cord was observed for and, when found, measurements were made of it. Ranges of motion were carried out while observation of the oblique cord was made. An oblique cord was found on 52.6% of sides. Gantzer's muscle was found on 55% of sides and, when present, had attachment into the oblique cord on five sides. The oblique cord was present on 13 sides with a Gantzer's muscle. Of the 20 sides with an oblique cord, no Gantzer's muscle was found on 10. The mean length of the oblique cord was 3.4 cm. In the majority of specimens, this cord tapered from proximal to distal. The proximal, middle, and distal widths of this structure had means 9, 7, and 4 mm, respectively. The oblique cord was found to travel approximately 45 degrees from a line drawn through the ulna and more or less traveled perpendicular to the insertion site of the bicipital tendon. This ligament was lax in the neutral position and with pronation became lax in all specimens. The oblique cord progressively became taut with increased supination from the neutral position and was maximally taut with the forearm fully supinated. Tautness of this cord was also found with distal distraction of the radius. Following the transection of the oblique cord, no discernable difference was observed in regard to maximal supination of the forearm or distal distraction of the radius. No obvious instability of the proximal forearm was found following transection of the oblique cord. Functionally, although the oblique cord may resist supination, it is unlikely that this structure affords significant stability to the proximal forearm, as it was often absent, of a very small caliber, and based on our observations, following its transection, the amount of supination of the forearm did not increase. Moreover, one would expect that this structure would never resist supination alone, as the larger overlying muscles would become taut prior to calling upon the action of this cord. Based on our findings, the function of the oblique cord appears insignificant in providing significant stability to the proximal forearm; however, further investigative studies are now necessary to confirm these data.

Aged↗
PubMed2007

Superficial temporal artery as an external landmark for deeper-lying brain structures.

Additional localizing superficial landmarks for intracranial structures can be of use to the neurosurgeon. This study was performed to evaluate the usefulness of the superficial temporal artery (STA) as an external landmark for deeper brain structures. Thirteen adult cadavers (26 sides) underwent latex injection of their STA bilaterally. Dissections were next carried out to identify this vessel. Once the STA and its frontal and parietal branches were skeletonized, craniectomies were performed and the underlying dura mater excised. Measurements were made between the frontal and parietal branches of the STA and deeper brain structures. The STA was found to branch on average 3 cm superior to the tragus. The bifurcation of the STA was found to commonly bifurcate at the level of the floor of the middle cranial fossa or superior temporal gyrus. The Sylvian fissure was found at a mean of 2 cm superior to the STA bifurcation. The angle between the frontal branch of the STA and the zygomatic arch had a mean of 37 degrees. The angle between the frontal and parietal branches of the STA had a mean of 87 degrees. At the level of the glabella, the frontal branch of the STA was on average 3 cm posterior to the frontal pole. The temporal tip was located a mean of 3.2 cm anterior to the frontal branch of the STA. The plane of the foramen of Monro was found to lie at a mean distance of 2.3 cm posterior to the frontal branch of the STA. The parietal branch of the STA was noted to travel more or less parallel with the central sulcus in all specimens and to travel an average of 2 cm posterior to this sulcus. At the level of the lateral attachment of the tentorium cerebelli, the parietal branch of the STA was found to travel a mean of 4.8 cm anterior to the entrance of the vein of Labbé into the transverse sinus. The parietal branch of the STA was also found to travel a mean of 4.2 cm anterior to the angular gyrus and 3.9 cm anterior to the supramarginal gyrus. Palpation or Doppler identification of the STA and its branches with subsequent mapping on the lateral cranium may prove useful as an additional superficial landmark for the neurosurgeon.

Aged↗
PubMed2007

Wilhelm Erb and Erb's point.

Wilhelm Erb is well known for his early contributions to the field of neurology and was an eminent physician of his time. One area described by him and that still bears his name is Erb's point. This point located just superior to the clavicle was used by Erb to transcutaneously elicit contractions of various proximal arm muscles with electrical stimulation. Many have mistakenly interchanged the terms "Erb's point" and "nerve point" when describing the point of emergence of the cutaneous branches of the cervical plexus near the posterior border of the sternocleidomastoid muscle. We present a brief history of Erb's adult life and review his original description of his supraclavicular point and contrast this to the so called nerve point of the posterior cervical triangle. Clinicians and anatomists should be aware of the discrepancy often found in the literature between these two terms.

Anatomy↗
PubMed2007

Cadaveric findings of persistent fetal trigeminal arteries.

Persistence of fetal intracranial arteries is rare. We review this anatomical literature regarding the persistence of the trigeminal artery and discuss the findings in two cadaveric cases both found to harbor this vessel. This anomaly should be considered by the clinician and anatomist who view imaging of the skull base. Additionally, the relationships between such an artery and other structures within the cavernous sinus should be understood by the neurosurgeon who operates in this region, e.g., transsphenoidal approaches to the skull base.

Aged↗
PubMed2007

Branches of the petrous and cavernous segments of the internal carotid artery.

Microsurgical approaches to the skull base require a thorough knowledge of the microvasculature of this region. Interestingly, most standard texts of anatomy do not mention the branches of the internal carotid artery as it travels through the temporal bone and cavernous sinus. Although small and with often conflicting descriptions, these arterial branches may be of significance when contributing to the vascular supply of such pathological entities as meningiomas and vascular malformations. Furthermore, multiple anastomoses exist between these branches and branches of the external carotid artery, thus providing a potentially important collateral circulation between these two systems and thus retrograde flow needed to maintain the patency of the distal internal carotid artery (ICA) when this vessel is obstructed proximally. We review the literature regarding these branches of the internal carotid artery and their clinical significance.

Carotid Artery, Internal↗
PubMed2007

Origins of the gonadal artery: embryologic implications.

The gonadal arteries are paired vessels that usually originate from the abdominal aorta at the level of second lumbar vertebra. In 5-20% of cases, the gonadal artery has a high origin (superior to L2) and in 5-6% of cases it originates from the main or accessory renal artery. The latter is referred to here as an aberrant gonadal artery. Ninety-eight kidneys of 50 healthy potential renal transplant donors were prospectively studied by conventional angiography. The renal artery, either main or accessory, was detected and individually injected to highlight their perihilar divisions and possible extrarenal branches. The gonadal arteries were recorded if they originated from the renal arteries. We found that 39% (n = 38) of kidneys had at least one accessory renal artery. In 14 sides (14% of kidneys), the gonadal artery (11 right and 3 left) originated from the renal artery, either main (n = 5) or accessory (n = 9). Ten out of 14 kidneys with an aberrant gonadal artery had an associated accessory renal artery. In nine cases, the gonadal artery originated from the accessory renal artery, and in one case, although it originated from the main renal artery, the same kidney had an accessory arterial supply. The results of this study demonstrate that aberrant gonadal arteries tend to originate from kidneys that possess an accessory arterial supply. We hypothesize that aberrancies of the gonadal artery are a part of a common embryologic error resulting in the persistence of the future accessory renal arteries. We believe that this study is the first to hypothesize and study such an association with these arterial anomalies of the renal pedicle.

Adult↗
PubMed2007

Video game epilepsy in the twentieth century: a review.

INTRODUCTION: Visually evoked seizures have been reported for almost 2,000 years. This source of seizure activity, however, seems to have increased recently with the advent of new technologies used for television and computer games. METHODS: The present paper reviews the literature regarding this interesting phenomenon. RESULTS: After our review, it does appear that visually evoked seizures have increased in frequency during the twentieth century. CONCLUSIONS: We believe that knowledge of visually evoked seizures may aid neuroscientists in further exploration of the pathophysiology of seizure activity and its related preventive measures. Further studies are necessary to prove the etiology of such seizure activity.

Adolescent↗
PubMed2007

Benign fibrous histiocytoma of the skull base. Case report.

The authors report the case of benign fibrous histiocytoma (BFH) of the skull base in an 11-month-old girl. During draining for a middle ear infection, the child was noted to have an anomalous mass in the skull base. On magnetic resonance imaging studies a soft-tissue mass of the skull base primarily involving the regions of the temporal and occipital bones was discovered. Results of a surgical biopsy were consistent with BFH. At the most recent follow-up examination--18 months postoperatively--the child was noted to be asymptomatic with no gross increase in tumor size.

Biomarkers, Tumor↗